This invention relates to a test head for an integrated circuit tester.
The test head of a conventional semiconductor integrated circuit tester may be used in conjunction with a wafer prober. The test head is typically placed directly above the wafer prober for sequentially testing wafers that are delivered to the test head from below. The test head houses pin electronics on rectangular pin electronics cards, and the pin electronics cards are disposed in the test head so that each card lies in a vertical plane with vertical and horizontal edges. Each card has pin electronics terminals distributed along its lower horizontal edge and these terminals are connected to the device under test (DUT) through a so-called pogo tower, a DUT board (or device interface board) and a probe card.
In operation of the test head, a large amount of heat is dissipated from the pin electronics. Heat is removed from the test head by inducing a flow of air over the surfaces of the pin electronics cards. The pin electronics cards may be arranged so that they radiate from a vertical axis, but heat removal is more efficient if the cards are disposed parallel to each other. For compactness, the cards may be arranged in two parallel rows.
It is desirable that the signal path length between a pin electronics terminal of a pin electronics card and the corresponding terminal of the probe card should be short and should be uniform over all the pin electronics terminals.
The distance between a pin electronics terminal of a pin electronics card and the corresponding terminal of the probe card depends on the position of the pin electronics terminal along the lower edge of the pin electronics card. In order to achieve the desired uniform signal path length, it is necessary to compensate for the variation in distance between the pin electronics terminals of the pin electronics cards and the corresponding terminals of the probe card. This can be accomplished by appropriately designing the pattern of conductive traces of the DUT board, but the DUT board is then more expensive than would otherwise be the case.
To increase heat removal efficiency, it would be desirable to provide an air collection plenum between the two rows of pin electronics cards, but this would increase the distance between the pin electronics terminals and the corresponding terminals of the probe card, exacerbating the problem of non-uniformity of signal path length.